1. Field of the Invention
The present invention relates to laryngoscopes, and particularly to an improved blade for a laryngoscope.
2. Description of the Related Art
While a laryngoscope may be used to visually examine the larynx, its more important function is to aid in endotracheal intubation. The need for intubation may arise during a controlled situation, such as surgery, or in a crisis situation when the patient is unable to breathe adequately and requires a resuscitation bag or mechanical ventilation. During intubation, a flexible tube is inserted through the nasal or oral cavity, passed through the larynx, and into the trachea for the administration of gases. The larynx may be viewed as a chamber bounded superiorly by the epiglottis, inferiorly by the vocal cords which cover the opening to the trachea, anteriorly by the thyroid cartilage or Adam's apple, and posteriorly by a portion of the pharynx. The epiglottis is a lamella or leaf-like plate of cartilage which extends dorsally like a loose lid over the larynx, helping to protect the trachea by preventing food from entering the trachea during swallowing.
In order to intubate the patient, the intubator (either a physician or paramedic) must visualize the epiglottis and the vocal cords to watch the tube go past the vocal cords of the patient. The laryngoscope generally comprises a handle, a blade which is used to move the patient's tongue out of the way and to lift the epiglottis to expose the vocal cords, and a light source to illuminate the glottis and vocal cords.
The two most widely used blades in the current state of the art are known as the Miller blade and the Macintosh blade. The Miller blade is a substantially straight blade with a curved tip, the curve commencing approximate 2 inches from the end of the blade. The Macintosh blade is a blade which is curved for substantially its entire length (U.S. Pat. No. 2,354,471 issued Jul. 25, 1944). In use the Miller blade is inserted along the longitudinal axis of the larynx past the epiglottis to lift it enough to visualize the vocal cords and slip the tube through the cords into the trachea. The Macintosh blade is inserted on a combination of the axis of the oral cavity and the longitudinal axis of the larynx, the tip being placed in the vallecula, which are shallow depressions in the membranous folds and tissue between the epiglottis and the root of the tongue. By applying an upward pressure at the vallecula, the epiglottis is raised enough to visualize the vocal cords.
While intubation may be done with the existing blades, several shortcomings in the existing blades have prompted various efforts to improve the blades. Efforts to improve the curvature of the blade are shown in U.S. Pat. No. 5,003,962, issued Apr. 2, 1991 to Choi, and U.S. Pat. No. 5,406,941 issued Apr. 18, 1995 to Roberts. Choi describes a blade having three straight segments, the second segment at a 20 degree angle to the first, and the third at a 30 degree angle to the second. The Roberts patent describes a flat, flexible blade, having a cam attached to one side of the blade so the curvature may be adjusted by rotating the cam. U.S. Pat. No. 3,856,001 issued to O. C. Phillips Dec. 24, 1974 describes a Jackson or straight blade having a U-shaped cross-section and a tip similar to the Miller blade, curving about 2 inches from its end.
Efforts to improve the tip are shown in U.S. Pat. No. 4,573,451, issued Mar. 4, 1986 to Bauman, and U.S. Pat. No. 5,603,688 issued Feb. 18, 1997 to Upsher. The Bauman patent describes a blade made of plastic or metal, thinned or hinged at the tip, with a push rod and a ratchet to change the angle of the tip. Upsher's patent shows a blade having a hollow tube in the blade for insertion of the endotracheal tube, with an extension of one side of the tip to prevent the natural curve of the endotracheal tube from causing the end of the endotracheal tube to leave the field of vision after exiting the hollow tube in the blade.
Efforts to improve the illumination of the larynx and vocal cords are shown in U.S. Pat. No. 3,638,644 issued Feb. 1, 1972 to Reick, and U.S. Pat. No. 3,771,514 issued Nov. 13, 1973 to Huffman, et al. The Reick patent shows a light bulb in the handle with a plastic light conduit extending through the blade. The Huffman patent shows a one-piece handle and blade, the blade having a prism mounted thereon for reflecting and diffusing the light.
U.S. Pat. No. 5,036,835 issued Aug. 6, 1991 to Filli describes a blade which slides to adjust the length of the blade. U.S. Pat. No. 5,065,738 describes a sheath fitting over the blade to protect the patient's teeth, gums, oral mucosa and epiglottis from damage during insertion of the laryngoscope.
Various patents show a disposable blade, including European Patent 0184588 published Jun. 18, 1986, describing a disposable blade with a light source in the handle; International Patent 94/03101 published Feb. 17, 1994, describing a disposable blade with the light source in the blade; and International Patent 97/17885 published May 22, 1997, showing a disposable blade with a channel in the blade for the passage of fluids.
Construction techniques for incorporating a channel or path for a bulb and light cable or guide are shown in U.K. Patent 2,102,294 published Feb. 2, 1983, describing two L-shaped members put together in overlapping fashion to form a channel for the light and cable, and U.K. Patent 2,102,679 describing a blade made by placing a fiber optic bundle in an injection mold and forming a plastic blade by injecting the mold with plastic.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus an improved laryngoscope blade solving the aforementioned problems is desired.
The present invention exploits the principle used by health care providers to widen the airway in preparation of intubation. When the head is in the normal anatomic position, the airway is narrow. It is therefore recommended that the intubator align the laryngeal and pharyngeal axes; unlike the present invention, in this position neither the Miller blade nor the Macintosh blade present the optimum angle for viewing and intubating the patient. Although the Macintosh blade is curved, the curvature is greater than the curvature of the airway, hence it does not permit optimal visualization of the vocal cords because the intubator can't see around the curvature of the blade. Moreover, with both the Miller blade and the Macintosh blade, the intubator has difficulty visualizing the tip of the blade, again due to the shape of the blade and the shape of the airway. Consequently the intubator has difficulty determining when the tip is in proper position.